1. The Field of the Invention
This invention relates to optically operated display equipment and more particularly of that class utilized to project images of varying sizes and at varying light intensities.
2. Description of the Prior Art
The prior art abounds with apparatus utilized to control camera or projection objects or parts thereof. U.S. Pat. No. 3,482,500 issued on Dec. 9, 1969 to O. Thomas teaches a control mechanism for a camera objective employing a motor rotationally coupled to a gear train which in turn engages a gear-like peripheral surface of a barrel of a zoom lens assembly. The barrel is utilized to vary the position of a lens. The patent to Thomas does not disclose any attempt to utilize the same or another motor to control an iris portion of the zoom lens apparatus.
U.S. Pat. No. 2,924,146 issued on Feb. 9, 1960 to F. G. Back discloses three elements of a zoom lens assembly, two being lenses and the third being an iris mechanism, rotationally coupled to independently operated motors by way of spur gears affixed about the barrels of the zoom lens apparatus. The teachings of Back, though applicable in concept to that of the present invention, fails to provide convenient simultaneous adjustment of the iris and zoom lens assembly and when utilizing remote control apparatus, fails to adequately signal an operator as to the size of the display image and the intensity thereof.
U.S. Pat. No. 3,889,282 issued on June 8, 1975 to S. Hashimoto discloses an interchangeable zoom lens having front and rear axially movable optical systems arranged so that they can be moved in opposite directions so as to vary the focal length, to wit, zooming, the front system being independently movable for focusing by means of a distance ring projecting forward providing a lens hood effect. The zooming control superimposes a displacement on the preset adjustment of the aperture by the aperture preset ring, and also modifies the maximum open position of the aperture adjustment mechanism. The teachings of Hashimoto, although utilizing a manually rotated zoom assembly, adapted primarily for use in cameras is radically different from the apparatus taught in the present invention, in that the aperture or iris assembly, of the present invention, is simultaneously varied whilst the focal length of the zoom lens apparatus thereof is being altered. The present invention however, teaches that the relative aperture size and the focal length may be altered in relationship to one another by having either the iris assembly or the zoom assembly cease rotation upon engagement with a stop element whilst permitting the remaining element to be varied, leading to a change in focal length without a change in aperture size, or conversely, a change in aperture size without a change in focal length.